Great start, but the format needs to be sorted. I would have like to see more background to the story to how they got to this point.
Author's response
I know. It was a bit of a struggle to post it all the first time, and I'm going back to fix the format part by part.
As for background, read Rorshcach's Blot's Omake "Harry Potter and the Accidental Harem" (http://www.fanfiction.net/s/2565609/59/Odd_Ideas). That's the background this story spun off of, along with canon.